MicroPython Forum (Archive)

I have been following the tutorial on the REPL prompt and can't get the prompt to appear.

On a Mac I have run screen /dev/tty.usbmodem* and this executes correctly but just gives me a totally blank window box. Whatever I do (pressing enter etc) I can't seem to get a Micro Python prompt >>> to type in anything. I have reread the manual (man screen) multiple times with no joy. The board is definitely connected and if I type CTRL-A CTRL-\ it disconnects successfully with the message [screen is terminating]. I tried sudo screen /dev/tty.usbmodem* as well but with the same result.

I also tried with a Raspberry Pi running Raspbian. Again screen /dev/ttyACM0 executes but again gives a blank box. It will disconnect correctly but I fail to get a prompt.

Could someone please advise what I am doing wrong in screen ? I am sure it is something basic! Thank you

Do you have a script running (uploaded through mass storage device, or on sd card)?

Thank you Frédéric! Yes I did have a script running. Have cleared this and now I can connect to screen and get the prompt. I knew I must have being doing something stupid!

Damien - you may want to put a comment on the tutorial for the REPL page to say make sure you are not running a script and have a blank main.py file before running screen for those like me

In fact, I just saw that you can get the prompt if you connect right after a reset (during a few second, it is possible).

Doing this, the script does not start. If you press CTRL-D, you get a soft reset, keeping the connection open, and so you can see errors and all print() from your script. Very usefull to debug things!

You should also be able to use Control-C to stop the running program and be dropped to the REPL prompt.

Ok, but as long as you was able to connect... If you try while the script is running, you can't even connect (the serial line is not created). Am I right? Or did I miss something too?

I thought that the serial line was created before the script runs, and that handling the characters was all interrupt based.